What is the Gut-Brain Connection?

By Laura McDaniel, RN

Early Fetal Development

Have you ever become sick to your stomach after hearing bad news? Or maybe you felt foggy headed or became anxious after eating a certain food? The brain and the "gut" (esophagus, stomach, small intestine and colon) are intimately connected with each other, and this link occurs very early in our lives.

During early fetal development, both your gut and your primary brain develop from the same clump of embryonic tissue. When this tissue divides, one piece grows into your central nervous system (brain and spinal cord). The other section becomes your Enteric Nervous System (ENS).

The Second Brain

The Enteric Nervous System (ENS) is embedded in the lining of the gastrointestinal system. Due to its incredible complexity, the ENS has been described as a "second brain" and contains the same number of neurons as the spinal cord.

Technically known as the enteric nervous system, the second brain consists of sheaths of neurons embedded in the walls of the long tube of our gut, or alimentary canal, which measures about nine meters end to end from the esophagus to the anus. The second brain contains some 100 million neurons, more than either the spinal cord or the peripheral nervous system. M Gershon MD. The Second Brain Harper 1998 P17n

In later stages of development, these two "brains" then become connected via a massive nerve – the vagus nerve.

The Vagus Nerve

The vagus nerve is the longest of all our cranial nerves and creates a direct connection between our brain and our gut. Vagus means "wandering" and this important nerve travels from the brain through many parts of the body, including the heart, lungs, stomach and ears. Among its functions is to provide vital information between the brain and the gut on how the body is digesting food. It also sends messages to the gut to contract the stomach and intestines to aid in this process.

The vagus nerve has also been shown to carry signals initiated by bacteria. Staphylococcus can attack the vagus nerve and induce vomiting. Salmonella infections have been shown to affect brain activity, a connection lost when the vagus nerve is severed.

The Role of Serotonin

90-95% of the body's serotonin lies in the gut. The serotonin that is housed in the gut acts as a neurotransmitter. It sends messages between nerve cells and helps regulate mood, sleep and learning and can influence our state of well-being. Serotonin also plays a critical role in digestion. The digestive process begins when a specialized cell, an enterochromaffin, excretes serotonin into the wall of the gut, which has at least seven types of serotonin receptors. These receptors, in turn, communicate with nerve cells to start digestive enzymes flowing or to start things moving through the intestines.

Serotonin also acts as a go-between, keeping the brain in the skull up to date with what is happening in the brain below (the gut). Such communication is mostly one way, with 90% travelling from the gut to the head.

Scientists are learning that the serotonin made by the enteric nervous system might also play a role in more surprising diseases: In a new Nature Medicine study (Scientific American is part of the Nature Publishing Group) published online February 7, a drug that inhibited the release of serotonin from the gut counteracted the bone-deteriorating disease osteoporosis in postmenopausal rodents.

"It was totally unexpected that the gut would regulate bone mass to the extent that one could use this regulation to cure – at least in rodents – osteoporosis," says Gerald Karsenty, lead author of the study and chair of the Department of Genetics and Development at Columbia University Medical Center.

Leaky Gut

A healthy digestive tract breaks down foods into small particles and releases these beneficial nutrients into the bloodstream. When the gut is not healthy and becomes too permeable, it becomes difficult to digest foods. The most difficult to digest foods are gluten, casein and soy. (Gluten is the protein found in wheat, barley and rye. Casein is the protein found in dairy products.) If the proteins in these foods are not digested properly, these large molecules, called peptides, can leak out of the small intestine and into the bloodstream where they do not belong.

This can affect the body in many ways:

- The ability to absorb valuable nutrients can be impaired
- Autoimmune reactions can be triggered
- Toxins may not be properly eliminated by the body and can affect brain function

The Gut-Brain Impact on Development and Health

Because of the direct gut-brain connection, it is no wonder the state of our gut has a huge impact on our physical, emotional and cognitive abilities. In the presence of excess bad bacteria, the presenting symptoms may be obsessive compulsive disorders, repetitive behaviors, decreased desire to socialize and mood swings.

- Talk About Curing Autism (TACAnow.org) reports 91% of children with autism have improvements in speech, learning, behavior and improved sleep on a gluten, casein and soy-free diet. Clients with autism are found to also have elevated peptides in their urine, indicating an inability to digest gluten and casein.

- Schizophr Res. 2011 May;128(1-3):51-5. Association between bovine casein antibody and new onset schizophrenia among US military personnel. "This is the first report to identify an association between the risk of schizophrenia and elevated antibodies to bovine casein prior to disease onset."

- Nutritional Neuroscience. 2010 June; 13(3): 135-43. Increased clostridia difficult infections found in samples of patients with schizophrenia and autism.

- Pediatrics. 2012 Feb; 129(2):330-7. The diet factor in attention-deficit/hyperactivity disorder. "A greater attention to the education of parents and children in a healthy dietary pattern, omitting items shown to predispose ADHD, is perhaps the most promising and practical complementary or alternative treatment of ADHD."

- The Lancet. Volume 377, Issue 9764 Pages 494-503, 5 February 2011 Effects of a restricted elimination diet on the behavior of children with attention-deficit hyperactivity disorder. "A strictly supervised elimination diet is a valuable instrument to assess whether ADHD is induced by food."


Celiac Disease is an autoimmune condition triggered by eating gluten. It damages the surface of the intestines, causing a permeability of the intestines and the inability to absorb certain nutrients. Several studies have shown a possible connection between celiac disease and some developmental disorders.

o Prim Care Companion CNS Disord. 2011; 13(3) Association of attention-deficit/hyperactivity disorder and celiac disease: a brief report.

o Gut. 1997 Apr; 40(4):492-6 Down's syndrome is strong associated with coeliac disease

o Neurology. 2012 Apr 18 Increased risk of epilepsy in biopsy-verified celiac disease: A population-based cohort study. "Individuals with CD    seem to be at a moderately increased risk of epilepsy."

o J Child Neurol. 2010 Jan; 25(1):114-9 Celiac disease presenting as autism. "It is recommended that all children with neurodevelopmental problems be assessed for nutritional deficiency and malabsorption syndromes."


In the 12 years I have worked with patients being treated for brain imbalances, a full spectrum of symptoms have been reported from these leaky gut phenomena. Some patients report brain fog, difficulty concentrating, mood swings, explosive temper, lack of speech or socialization, and even hallucinations and psychotic thoughts when certain foods are ingested.

Ways to Heal

The best ways to support your second brain (the gut) and promote healing:

- Avoid offending foods. Gluten, casein and soy are the most common offenders. Corn, sugar and nuts can also be problem foods.
- Reduce inflammation with curcumin and aloe. Curcumin is the active ingredient in the spice turmeric.
- Replace good bacteria in the gut with probiotics. Probiotics are beneficial or "good" bacteria.
- Facilitate digestion of fats, carbohydrates and proteins with broad spectrum digestive enzymes that contain DPPIV. Digestive enzymes break down foods that you eat into substances that your body can utilize, and different enzymes work on different foods, i.e. some digest fats, some digest proteins, and others digest carbohydrates.
- Kill bad bacteria, parasites and yeast overgrowth in the gut. Specialty stool, urine and blood tests can help determine what organism imbalances are present.
- Take omega 3 and omega 6 fatty acids to promote healing.

Depending on each individual's situation, the outcome from the healing process can be sudden and profound or slow and steady.


Laura McDaniel RN is the owner of Wyndgate Health. Laura may be reached through her website, www.wyndgatehealth.com. At Wyndgate Health, clients undergo a detailed history, physical and laboratory testing by a nurse practitioner or physician's assistant. The patient is then prescribed a personalized prescription of supplements and dietary recommendations.